Cathode-ray tube envelope



Feb. 26, 1957 R. H. DALTON ETAL CATHODE-RAY TUBE ENVELOPE Filed April15, 1954 INVENTORS fast-er 6! $191.70 41m PAY/womb O. V066 5y la .11NE).

United States Fatent (ZATHODE-RAY TUBE ENVELOPE Robert H. Dalton andRaymond O. Voss, Corning, N. Y., assignors to Corning Glass Works,Corning, N. Y., a corporation of New York Application April 13, 1954,Serial No. 422,826 4 Claims. (Cl. 220-2.3)

The present invention relates to glass-to-metal seals whereincomplementary endless surfaces of two glass parts, such for example asthe funnel and panel members of a television picture tube envelopeassembly, may be separately joined to metal strip and the sides of thestrips opposite to which the members are sealed brought together andthen sealed to one another to provide a hermetic seal between the paneland funnel members.

Glasses are customarily sealed to metals and alloys by melting the glassand contacting it with the metal. Such seals may be classified as thosein which the expansion coefiicients of the glass and the metal aresubstantially matched and those in which the expansion coefficients aredissimilar.

Most glass-to-metal seals are of the first type, in which the expansioncoefficient of the glass between its setting point and room temperatureis so close to that of the metal through the same temperature range thatdifferences in contraction of the metal and the glass on cooling do notcause breaking stresses in the glass. When the expansion cocfiicientsare so matched, the thickness of the metal member at the seal isrelatively unimportant. However, when the expansion coefficients of theglass and the metal are dissimilar, the thickness of the metal member atthe seal is very important. Successful sealing with mismatched expansioncoefiicients requires that the metal member be very thin at the area ofthe seal.

It is the latter type of seal employing aluminum sealing strips withwhich the present invention is concerned. From our copending applicationSerial No. 219,430, filed April 13, 1951, now Patent No. 2,707,850, ofwhich this application is a continuation-in-part it is known that analuminum strip can be successfully sealed or welded, Without melting ofthe aluminum, to a glass having a working point above the melting pointof aluminum by the use of a sealing glass having a working point belowthe melting point of aluminum and a thermal expansion coefiicient notmore than x10 per C. different than the glass, provided the thickness ofthe aluminum member at the area of sealing or welding is not over 7mils.

It has occurred to us that two glass members, such for example as thepanel and funnel members of a television picture tube, as ordinarilyadapted to be directly welded to one another to form a completed picturetube envelope, can conveniently have their sealing surfaces separatelyjoined by a suitable sealing glass to aluminum sealing strips, as taughtby the above copending application, after which such parts may bebrought into register and the aluminum strips welded to one anotheralong an area laterally disposed from the glass-aluminum seals tocomplete a seal between such parts.

It has been discovered however that it is extremely difiicult toreliably weld two 7 mil thickness aluminum strips to one another. Theproblem was finally solved according to this invention by making eachstrip, in transverse cross-section, of approximately 7 mils thickness inthe area to be occupied by the glass seal and by impart ing to the areaof the strips to be sealed to one another such added thickness as isfound to be suitable for satisfactorily welding them to one another.Pressure tight seam weld seals can be made between aluminum strips ofabout 10 mils or greater thickness in a manner fully described on pages703 and 704 of the Welding Handbook, third edition, published byAmerican Welding Society.

It would appear at first blush that a seal of the fore going characterwould afiord a rather weak mechanical coupling between a picture tubepanel member and its companion funnel member. Since, however, thepicture tubes are evacuated to a high degree the panel and funnelmembers are pressed into rigid relationship by external air pressure,and therefore mechanical rigidity of the seal itself need not be reliedupon for imparting mechanical strength to the envelope.

The accompanying drawing illustrates in Fig. l a side elevation of apicture tube envelope assembly embodying the invention.

Fig. 2 is an enlarged fragmentary view in section of a preferred form ofseal between the panel and funnel members of such an assembly.

Fig. 3 is a perspective view of a greatly enlarged fragment of a sealingstrip employed in accordance with the invention.

Fig. 4 is a view similar to Fig. 2 illustrating an alternativeembodiment of the invention.

Fig. 5 is a view similar to Fig. 4 illustrating a further alternativeembodiment of the invention.

Referring to the drawing in detail, numeral 11 desighates the envelopepanel member, 12 the funnel member thereof, and 13 and 14 theirrespective sealing strips.

The sealing strips for the panel and funnel are identical andaccordingly a description of a typical sealing strip 33 shown intransverse cross section in Fig. 3 will suffice. Such strip is seen tohave a relatively thick outer por tion and an adjoining relatively thininner portion. One face 35 of the strip is a planar throughout the stripwidth, whereas the oppositely disposed face of the strip hasconcentrically disposed planar surfaces 36 and 37 at two levels joinedto one another as by a beveled annular surface 38.

In the form of the invention illustrated in Fig. 2 the panel portion 21of a tube envelope is sealed to surface 25 of the thin cross-sectionalportion of an aluminum strip or ring 23 having an integrally adjoiningthick crosssectional portion 27. A similar but oppositely disposed ripor ring 24 having a thick portion 28 is in a similar fashion sealed tothe funnel portion 22 of the tube en velope. The thick strip portions 27and 28 are then welded to one another to establish a hermetic sealbetween the funnel and panel members.

In the form of the invention illustrated in Fig. 4 the strips 46 and 47have the inner regions of their surfaces 43 and 44, respectively, sealedto the panel 41 and funnel 42 after which the panel and funnel arearranged With their strips in sealing relation and with a gasket 45interposed between opposing surfaces 48 and 49 thereof. The abuttingsurfaces opposite surfaces 43 and 44 are then Welded to one another toeffect the hermetic seal. Obviously, the gasket 45 reduces point loadingalong the seal line when the finished tube is evacuated and isconveniently made of a thickness corresponding to the spacing betweensurfaces 48 and 49 to reduce distortion of the strips along the line ofjuncture of their thick and thin portions.

The form of the invention illustrated in Fig. 5 is similar to that ofFig. 4, except that the gasket 45 of Fig. 4 has been replaced by twogaskets 55 having sandwiched therebetween a support 57 projecting intothe envelope for accommodating a color viewing-screen assembly.

Patehtedl 'b. 26, 1957 Support 57 is provided at spaced intervals withstuds such as 56 for attachment of such an assembly thereto.

As will be understood, this invention is equally applicable to eithercircular or non-circular including the socalled rectangular-type picturetubes, the glass-sealing portions of the metalsealing elementsbeing-merely conformed to the outline of the glass surfaces to'whichthey are to bebutt-sealed.

It should be further understood that, although the shape of the panelsillustrated closely follows that embodied in commercial all-glassblack-and-white picture tubes, the invention is not limited in thisrespect, since sealing strips embodying the invention can with equalfacility .be sealed to shallow-walled, concave-convex, or substantiallyfiat panels such as are ordinarily employed in metal-funnel picturetubes.

What is claimed is:

1. An article of manufacture comprising two glass members havingcomplementary endless planar sealing surfaces facing one another, twometal strips piled one upon the other and arranged in part between suchsurfaces andhaving planar sealing surfaces complementary to the sealingsurfaces of said members, each strip having a seal portion sealed to theadjoining member sealing surface, said strips having portions that arethick relative to any of the portions thereof that are sealed to theglass members, said relatively thick portions projecting outwardly fromthe lateral border outlines of such seal portions in planes parallelthereto and being hermetically joined to one another in a planeintermediate to those occupied by the respective glass-metal seals.

2. A television picture tube envelope comprising two glass parts havingplanar endless sealing surfaces joined to one another through the mediumof a seal arranged between such parts, said seal including twocomplementary fiat strips of aluminum piled one upon the other, eachsuch strip in any transverse cross-section of the seal having inner andouter regions in the same plane, one being thick relative to the other,each of said sealing surfaces being sealed to a surface of the thinnerregion of a 'difierent one of said metal strips, and adjacent surfacesof the thicker regions of said strips being sealed to one another.

3. A picture tube envelope such as defined by claim 2 wherein thethickness of each strip throughout the region which is sealed to theglass part does not exceed 7 mils and in the region which is sealed tothe other strip is substantially over 7 mils in thickness.

4. A picture tube such as defined by claim 3 wherein the surfaces of thestrips to which the parts are sealed are planar throughout the stripwidth so that a space corresponding to the difference in thickness ofthe inner and outer region of the strips remains between the thinnerportions of said strips, and a cushion occupying such space.

References Cited in the file of this patent UNITED STATES PATENTS2,423,066 Gibson June 24, 1947 2,531,623 .Hale et'al. Nov. 28, 19502,635,205 Olson Apr. 14, 1953

